Press the sauté button on your Instant Pot. Add olive oil, then brown the chicken breasts on both sides (2–3 minutes per side). Work in batches if needed.
Cancel the sauté function. In a small bowl, whisk together Dijon mustard, honey, wholegrain mustard, soy sauce, garlic powder, salt, and pepper.
Pour the sauce over the chicken in the pot. Close the lid, set the valve to sealing, and pressure cook on high for 10 minutes.
Allow a natural pressure release for 5 minutes, then switch to quick release for the remaining pressure.
Remove the chicken and press sauté again. Mix water and cornstarch in a small bowl, stir into the sauce, and let it bubble for 2–3 minutes until slightly thickened.
Return the chicken to the pot or serve sliced with sauce spooned over top. Pair with mashed potatoes, rice, or something green if you’re feeling healthy.